The present invention is directed to a sensing tip for a gas leak detector for detecting the presence and location of leaks of refrigerant gases such as halogen used in refrigeration systems.
A halogen gas leak detector is disclosed in U.S. Pat. No. 4,488,118 to Jeffers, et al. That detector operates by applying a high voltage across a pair of electrodes provided in a sensing tip to generate a continuous corona current. The magnitude of the corona current varies in response to changes in concentration of halogen gas, and the concentration of gas is determined by sensing changes in the corona current. The sensing tip of the detector, which is shown in FIG. 3 of the Jeffers, et al. patent, incorporates a pointed electrode provided in the interior of a conductive housing having a cylindrical portion terminating in a hemispherical portion. A high voltage is provided across the electrodes to induce a corona current to flow through the electrodes.
A disadvantage of the sensing tip used in the Jeffers, et al. detector is that the corona may form between the pointed electrode and various points on the interior surface of the conductive housing, and may "jump about" by forming between the pointed electrode and a first location on the interior surface of the housing, and then forming between the pointed electrode and a different location on the interior housing surface. As the corona jumps about, the magnitude of the corona current may be affected, so that the magnitude of the corona current will not necessarily reflect accurately the concentration of halogen gas present in the vicinity of the sensing tip. Another disadvantage of the Jeffers, et al. sensing tip is that its particular structure may require an unduly high voltage to be used to generate the corona.
U.S. Pat. No. 4,609,875 to Jeffers discloses a sensing tip for a gas detector having a different structure. The sensing tip, shown in FIG. 4, includes a wire electrode provided within a generally cylindrical outer conductive housing. A conductive tube is provided in the interior of the housing, and the conductive tube is electrically separated from the conductive housing via an insulating tubular casing. A high voltage is provided across the first and second electrodes to induce a corona current to flow through the electrodes.